1. Field of the Invention
The invention relates to an organic electroluminescent device, and more particularly, to an electroluminescent device having an improved sealing structure.
2. Description of the Related Art
Electroluminescent devices have advantageous features suitable for next generation display devices. For example, electroluminescent devices have a wide viewing angle, a high contrast ratio and a high response speed. Electroluminescent (EL) devices are classified as inorganic EL devices and organic EL devices based on the materials which form the light-emitting layers.
FIG. 1 shows an organic EL device disclosed in U.S. Pat. No. 6,489,719. The disclosed organic EL device 1 comprises a substrate 2 having a positive electrode 3, a negative electrode 5 and a light-emitting layer 4 disposed between the positive electrode 3 and the negative electrode 5, and a sealing member 6 for sealing the substrate 2. Since the characteristics of the light-emitting layer 4 of the organic EL device deteriorate when exposed to moisture, it is necessary to isolate the light-emitting layer 4 from the moisture in the air.
Even if the substrate 2 and the sealing member 6 provide isolation, the sealing between the substrate 2 and the sealing member 6 is not perfect because of the physical properties of the adhesive 7 applied to adhere the sealing member 6 to the substrate 2. Thus, in order to minimize the amount of moisture infiltrating into the light-emitting layer 4 through the adhesive 7, it is preferable to reduce the thickness of the adhesive 7. In this case, however, there is a limit in reducing the thickness of the adhesive 7 because the adhesive 7 should be sufficiently applied to the substrate 2 and/or the sealing member 6 for the purpose of removing a gap therebetween. Consequently, in the organic EL device shown in FIG. 1 in which the gap (T) between the substrate 2 and the sealing member 6 is equal to the thickness of the adhesive 7 applied, it is difficult to satisfactorily prevent moisture in the air from infiltrating into the light-emitting layer 4, resulting in a shortened life of the organic EL device.